Media streaming from a server in the Internet to a plurality of clients via unicast connections has limitations due to a bandwidth ceiling of the network connections at the server.
However, media streaming in a peer-to-peer system alleviates this limitation by allowing a user to receive media content from any peer which has content instead of limiting the content dissemination capability to the server only.
Therefore, peer-to-peer (p2p) systems have become increasingly popular for applications like file sharing and media streaming. Several of such systems in use today employ different protocols and mechanisms for data dissemination amongst the peers.
The participants or hosts in a p2p system are typically heterogeneous in both their upload and download bit rates, also called upload and download bandwidths. Home DSL connections, for instance, tend to have a higher downlink bandwidth than uplink bandwidth. For example, a user connected to a DSL broadband interface can use a 1 Mbps download bandwidth and a 128 kbps upload bandwidth. Thus, for streaming of media the hosts in the Internet may need to cooperatively send media contents to a receiving peer owing to the lack of sufficient upload bandwidth to match the playback rate of the media stream.
Unlike on-demand content, live video streams have characteristics of time dependent utility of data blocks. In addition, unlike data file sharing, a receiving peer should be able to receive contiguous stream blocks which are then played-back by the host. Hence a scheme like Bittorrent described in B. Cohen, “Incentives build robustness in bittorrent,” proceedings of the 1st workshop on Economics of Peer-to-Peer Systems, June 2003, which performs exchange of random data blocks may not work well for multimedia streaming.
Several p2p multicast solutions, for instance as proposed in V. Padmanabhan et al., “Distributing streaming media content using cooperative networking,” ACM NOSSDAV, 2002, are based on building an overlay tree rooted at the source and dissemination of content to all the peers in the tree. However such approaches face the challenges due to disconnections caused by leaving of peers from the topology. Several measures to troubleshoot the problem via establishing multiple paths and multiple trees have been proposed in works like J. Silber, S. Sahu, J. Singh, and Z. Liu, “Augmenting overlay trees for failure resiliency,” IEEE Global Telecommunications Conference 2004.
Gossip based mechanisms have been investigated for their utility for peer to peer media streaming dissemination of data in a peer to peer system. These involve spreading of media blocks in a topology, in a manner like infectious virus spread in a population. As such a gossip pattern is followed by the hosts, the data block is eventually spread to all peers in the topology. The conformity of gossip based protocol to media streaming applications has been discussed in S. Verma, and W. Ooi, “Controlling gossip based protocol infection pattern using adaptive fanout,” International Conference on Distributed Computing System, 2005.
In U.S. Pat. No. 6,980,518 B1 Sun et al. describe a multicast messaging system employing a gossip based method for recovery of missing messages. The recovery mechanism involves soliciting retransmission of missing messages using gossips.